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Lepton Number and Lepton Flavour Violation

Lepton Number and Lepton Flavour Violation. Search for Majorana neutrinos in B-decays , lepton flavour violation in  -   -  -  + and baryon number violation with LHCb  seen Paul Seifert's talk today. LHCb collaboration. 54 institutions, 15 countries.

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Lepton Number and Lepton Flavour Violation

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  1. Lepton Number and Lepton Flavour Violation Search for Majorana neutrinos in B-decays , lepton flavour violation in- --+ and baryon number violationwith LHCb seen Paul Seifert's talk today LHCb collaboration 54 institutions, 15 countries

  2. Introduction Lepton Number Violation • No known symmetry associated with Lepton Number Conservation. • Gauge symmetry is behind electric charge conservation. • New Physics models such as those with Majorana neutrinos, • or LR symmetric models with doubly charged Higgs boson • can violate LN conservation.LHCb has searched for B-  +- - • and B-  K+- - Phys. Rev. Lett. 108, 101601 (2012) • Such decays have previously been searched for: • - Ξ-pμ-μ-HyperCP • D. Rajaran et al. Phys. Rev. Lett. 94, 181801 (2005) • - Bhe+μ-, he+e+, he+μ+,hμ+μ+ h=π,K,ρ,K* CLEO • K.W. Edwards et al. Phys. Rev. D65, 111102 (2002) • - 0νββ excellent review: • J. J. Gomez-Cadenas et al. Riv. Nuovo Cimento 35, 29 (2012) • - pp  (e+e+,e+μ+,μ+μ+) + X , high mass SS dileptons ATLAS • G. Aad et al. J. High Energy Phys. 10 (2011) 107.

  3. LHCb detector overview and performance Search for B-  +- - , B-  K+- - , B-  Ds+( ϕ(K+K-)π+ )-- B-  D+(K-+π+)-- , B-  D*+(D0+)- - , B-  D0(K-+)+- -

  4. B+ K μ+ μ- d~1cm B-Vertex Measurement B0 → J/Ψ (μ+μ-) K+ s(t) ~40 fs Primary vertex Proper-time resolutionst= 40 fs Vertex Locator (VELO) • Vertexing: • trigger on impact parameter • measurement of decay distance (time)

  5. Momentum and Mass measurement : Tracker OT TT LHCb [LHCb-CONF-2011-049] IT 8276 signal TT • TT and Inner Tracker: silicon micro-strips ~ 200 μm pitch. 12 m2 of silicon 4 layers with (0º, +5º,-5º, 0º) stereo angle. • Outer Tracker: drift chamber with 5 mm diameter straws gas Ar/CO2/O2 (70:28.5:1.5). • Resolution: D p/p= 0.4–0.8% (2–100 GeV/c). • Bs J/yf selection (J/y  m+m-, f  K+K-):s(mB) = 7 MeV/c2 (LHCb). • ~ 20 MeV/c2 (ATLAS/CMS) yields/pb-1 and S/B lower.

  6. Particle Identification RICH: K/p identification using Cherenkov light emission angle Bs → Ds K ,K Bs KK : 96.77 ± 0.06% pK : 3.94 ± 0.02% K K Ds  Primary vertex btag  RICH1: 5 cm aerogel n=1.03 , 4 m3 C4F10 n=1.0014 Pure sources of K and π given by D*+D0π+ , D0K-π+ RICH2: 100 m3 CF4 n=1.0005

  7. Particle identification: Calorimeters and L0 trigger e h ECAL (inner modules): σ(E)/E ~ 8.2% /√E + 0.9% • Calorimeter system : • Identify electrons, hadrons, π0 ,γ • Level 0 trigger: high ET electron and hadron

  8. Muon identification and L0 trigger B+ K μ+ μ- d~1cm m • Muon system: • Level 0 trigger: High Pt muons • pure muon sample from J/Ψ μ+μ- • μ-ID requirement applied to only one Primary vertex

  9. Search for Lepton Number Violation at LHCb Impressive limits to date from nuclear 0- decay on electrons: O(1025) years. Yet heavy quark mesons could undergo the same process with muons: Phys. Rev. D 85, 11204 (2012) arXiv:1201.5600v2 Virtual Majorana neutrino a) Resonant neutrino production b) Vub b c - Annihilation W-  N c) W- New - ¯ Vcb ¯ u d Also resonant production

  10. Limits from B-factories Belle results on B  D+l-l- Based on 772106 BB events at (4s), collected with the Belle detector at KEKB • BaBar results on B  h+l-l- with h=K, • Based on 471106 BB events at (4s), collected with • the BaBar detector at SLAC • Event selection similar to other B analysis. B mass and energy • calculated in center of mass system using Ebeam constraint

  11. Analysis general aspects Phys. Rev. Lett. 108, 101601 (2012) Phys. Rev. D 85, 112004 (2012) • Search for the decays • B-  +- - , B-  Ds+- - , B-  D+- - , B-  D*+- - , B-  D0+- - • using 0.41 fb-1 • Neutrinos are assumed to have a very narrow width compared to detector resolution. • Limits calculated asuming phase space, and also as function of neutrino mass • Signal yields are normalised to B channels with known branching fractions with • the same number of muons in 3-body and 5-body final states B- J/ K- J/  +- B- (2s) K- (2s)  + - J/ Total efficiency + - K- : 0.99  0.01 % Total efficiency + - + - K- : 0.078  0.002 %

  12. Majorana neutrinos B- +- - • B-  +- - • K// misid rates from D* +D0(K-+) • K0s and J/   • Peaking background from misid • B-  J/ K- and B-  J/- (2.5 evts) • Combinatorial background from • fit to the sidebands (5.3 evts) • Many systematics cancel in ratio to • normalisation channel

  13. Majorana neutrinos B- D+(*)- - Phys. Rev. D 85, 112004 (2012) • B-  D+- - , B-  D*+- - • Total efficiencies are 0.099  0.007 % and 0.066  0.005 % • D+ reconstructed via decay to K  , D*+ reconstructed via D0( K) • Any value of MN (virtual neutrinos) 6 evts 6.9  1.1 backg. 5 evts 5.9  1.0 backg. Total systematics : 8.8 % (D+ ) , 8.2 % (D*+) Dominated by branching ratios of normalization channels and trigger efficiencies Limits determined using and taking the vaue in which such probability is 0.05 (95 % C.L.)

  14. Mass and lifetime acceptance for on-shell Majorana neutrinos Finite neutrino lifetimes ignored so far (except for off-shell production) Sensitivity is lost for lifetimes longer than 10-10s to 10-11s. Mass resolution Neutrino mass acceptance B-+-- B- Ds+-- B- D0+--

  15. Systematic uncertainties for B-  DX--

  16. Systematic uncertainties for B- +- -

  17. B- Ds+- - and B- D0 +- - • B-  Ds+- - • Ds reconstructed via • decay to KK • Heavy neutrino can • decay to Ds+- • Ds+ decay tracks form a • vertex with - candidate • then a detached vertex • with second - (B-) • B-  D0+- - • D0 reconstructed via • decay to K • MN spectra consistent • with polynomial backgs. • estimated from sidebands MN Phys. Rev. D 85, 112004 (2012)

  18. Mass-dependent Majorana neutrino limits B-  +- - B-  Ds+- - B-  D0+- - • Upper limits (95% C.L.) are set at • each MNmass by searching a signal • within  3N in small steps. Phys. Rev. D 85, 112004 (2012) • For B-  D+(*)- - , limits • on the coupling require calculation • of hadronic form factor • (as for 0 decay) . • A model dependent calculation2 • was used for B- D0+-- , but • the mode +-- is more sensitive. 2 D. Delepine, G. Lopez Castro, and N. Quintero, Phys. Rev. D84 (2011) 096011, arXiv:1108.6009.

  19. Limits on Majorana coupling |V4 | Phys. Rev. D 85, 112004 (2012) B-+-- B   LHCb Mass dependent upper limits on the coupling |V4 | of a 4th generation Majorana neutrino to a muon and virtual W 1. 1A. Atre, T. Han, S. Pascoli, and B. Zhang, JHEP 05 (2009) 030, arXiv:0901.3589.

  20. Summary on LNV in B decays a BaBar,Phys. Rev. D 85, 071103 (2012) b CLEO, Phys. Rev. D 65, 111102 (2002) c Belle, Phys. Rev. D 84, 071106(R), (2011) d LHCb, CERN-PH-EP-2012-006, arXiv:1201.5600 (2012) e LHCb, Phys. Rev. Lett. 108 101601 (2012)

  21. Summary of LNV and LFV at LHCb • neither lepton number violation nor lepton flavour violations • observed yet • heavy quark and lepton decays provide good probes for • Lepton Number & Flavour Violation. Excellent sensitivity achieved • at B factories. • LHCb extends knowledge on forbbiden B decays • in LNV processes to 10-6…-8, establishing best limits on the coupling • |V4| of a 4th generation N to W, using B   • LHCb is approaching B factories for   • first measurement at hadron colliders: < 7.8 × 10-8 95% C.L. • LHCb has set limits ( 10-7)for the first time on  (B –L) = 0 • decays - p̅-+and - p-- Only up to 1.0 fb-1 used by LHCb, currently 3.0 fb-1 on tape

  22. THANKS

  23. Limits from B factories

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